Various embodiments of a respirator that includes a harness, a mask body, and an exhalation valve are disclosed. The exhalation valve can include a valve seat and a flexible flap that is in engagement with the valve seat. The flexible flap can have one or more materials that can cause the flap to flash when moving from a closed position to an open position or vice versa. The flashing valve can make it easier for a user to ascertain whether the valve is operating properly.